In distribution transformers it has been the general practice to include a secondary circuit breaker or a load sensing fuse to deenergize the transformer secondary when the secondary winding is subject to overload conditions. The secondary breaker must be fairly large because of the currents encountered in the secondary circuit and as a result adds significantly to the cost of the transformer. Load sensing fuses are conventionally one shot devices which require replacement on fusing as well as producing a substantial increase in the temperature of the dielectric fluid.